wifi: cfg80211: validate rx/tx MLME callback frame lengths before access

cfg80211_rx_mlme_mgmt() and cfg80211_tx_mlme_mgmt() call tracepoints
before rejecting frames shorter than the frame-control field. After
that, they only require len >= 2 before dispatching into subtype
handlers that assume their fixed fields are present.

The frames that trip this are not shorter than 2 bytes; they are short
relative to their subtype. mwifiex is a concrete in-tree example on the
length side: mwifiex_process_mgmt_packet() only requires a 4-address
ieee80211_hdr plus the 2-byte firmware length prefix before handing the
frame to cfg80211_rx_mlme_mgmt(). After stripping the length prefix and
removing addr4, pkt_len can be exactly 24: a bare 3-address management
header with no reason-code body. The existing WARN_ON(len < 2) does not
fire on such a frame, and cfg80211_process_deauth() then reads
u.deauth.reason_code as a two-byte access starting at offset 24,
immediately past the 24-byte buffer.

Add a frame-control length gate, then validate each subtype's minimum
frame size in an if/else-if chain that mirrors the dispatch logic. Trace
only after the frame is known to be well-formed.

Side effects of this change:
 - The WARN_ON(len < 2) is dropped. It only guarded the frame_control
   read, never the subtype fixed fields, and it does not fire on the
   frames that actually trigger the out-of-bounds read (which are >= 2).
   The len >= 2 check is kept as the guard before dereferencing
   frame_control, but without the warning: these are exported callbacks
   and a malformed frame from a driver should be dropped silently rather
   than backtraced.
 - cfg80211_tx_mlme_mgmt() previously routed every non-deauth subtype
   through disassociation handling; it now silently ignores unrecognised
   subtypes.

Assisted-by: Codex:gpt-5.5
Assisted-by: Claude:claude-opus-4.8
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260707025336.22557-1-enderaoelyther@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/wireless/mlme.c b/net/wireless/mlme.c
index 2a2c173058bacada2f36a05f88742b487e8f60c8..acc749eee2fea8579fef853003311898b809575f 100644 (file)
--- a/net/wireless/mlme.c
+++ b/net/wireless/mlme.c
@@ -151,19 +151,35 @@ void cfg80211_rx_mlme_mgmt(struct net_device *dev, const u8 *buf, size_t len)
 {
        struct wireless_dev *wdev = dev->ieee80211_ptr;
        struct ieee80211_mgmt *mgmt = (void *)buf;
+       __le16 fc;
 
        lockdep_assert_wiphy(wdev->wiphy);
 
-       trace_cfg80211_rx_mlme_mgmt(dev, buf, len);
+       if (len < sizeof(fc))
+               return;
+
+       fc = mgmt->frame_control;
 
-       if (WARN_ON(len < 2))
+       if (ieee80211_is_auth(fc)) {
+               if (len < offsetofend(struct ieee80211_mgmt, u.auth.status_code))
+                       return;
+       } else if (ieee80211_is_deauth(fc)) {
+               if (len < offsetofend(struct ieee80211_mgmt, u.deauth.reason_code))
+                       return;
+       } else if (ieee80211_is_disassoc(fc)) {
+               if (len < offsetofend(struct ieee80211_mgmt, u.disassoc.reason_code))
+                       return;
+       } else {
                return;
+       }
+
+       trace_cfg80211_rx_mlme_mgmt(dev, buf, len);
 
-       if (ieee80211_is_auth(mgmt->frame_control))
+       if (ieee80211_is_auth(fc))
                cfg80211_process_auth(wdev, buf, len);
-       else if (ieee80211_is_deauth(mgmt->frame_control))
+       else if (ieee80211_is_deauth(fc))
                cfg80211_process_deauth(wdev, buf, len, false);
-       else if (ieee80211_is_disassoc(mgmt->frame_control))
+       else
                cfg80211_process_disassoc(wdev, buf, len, false);
 }
 EXPORT_SYMBOL(cfg80211_rx_mlme_mgmt);
@@ -216,15 +232,28 @@ void cfg80211_tx_mlme_mgmt(struct net_device *dev, const u8 *buf, size_t len,
 {
        struct wireless_dev *wdev = dev->ieee80211_ptr;
        struct ieee80211_mgmt *mgmt = (void *)buf;
+       __le16 fc;
 
        lockdep_assert_wiphy(wdev->wiphy);
 
-       trace_cfg80211_tx_mlme_mgmt(dev, buf, len, reconnect);
+       if (len < sizeof(fc))
+               return;
 
-       if (WARN_ON(len < 2))
+       fc = mgmt->frame_control;
+
+       if (ieee80211_is_deauth(fc)) {
+               if (len < offsetofend(struct ieee80211_mgmt, u.deauth.reason_code))
+                       return;
+       } else if (ieee80211_is_disassoc(fc)) {
+               if (len < offsetofend(struct ieee80211_mgmt, u.disassoc.reason_code))
+                       return;
+       } else {
                return;
+       }
+
+       trace_cfg80211_tx_mlme_mgmt(dev, buf, len, reconnect);
 
-       if (ieee80211_is_deauth(mgmt->frame_control))
+       if (ieee80211_is_deauth(fc))
                cfg80211_process_deauth(wdev, buf, len, reconnect);
        else
                cfg80211_process_disassoc(wdev, buf, len, reconnect);